Prior to the present invention, nuts have been mounted on metal support plates or sheets by a machine press compacting the nut into an aperture and forcing malleable metal of the sheet into a nut-circumscribing recess located beneath an upper nut edge overhanging and overlapping the adjacent sheet surface next to the aperture. Such method thus resulted in a clamped-in nut-form bradded article which under excessive or repeated normal extraction pressures resulting from objects supported by screws mounted in the nuts, resulted too frequently in the nut being torn from its clamped-in seat within the aperture. Also, to prevent the clamped-in nut from revolving within the aperture seating structure of the sheet, the prior art companies have sometimes serrated a portion of the nut's circumscribing wall-edge so that it binds when the nut is pressed into its seated clamped-in position within the aperture. Another approach to prevent the clamped-in nut from twisting or turning in its seating aperture structure, has been to pre-form the nut to have an upper circumscribing edge of other than circular shape, such as hexagonal so that when the nut is compacted into the aperture, the hexagonally shaped nut-edge is bradded into the malleable metal of the surface of the sheet. While such nuts effectively prevent twisting or turning of the nut in its seated state, they never-the-less still have the low resistance to accidental extraction noted-above. Also of great significance, the manufacturing costs of such specially-shaped nuts is high, with a resulting high sales price for the finished product.
As is typically shown in the U.S. Pat. No. 4,095,327, the prior art presses the nut into a seated state within an aperture within the aperture-forming structure of the aperture. This patent illustrates still another approach for clamping the seated nut into its position by bending-over upper circumscribing aperture edge structure onto the top edge of the seated nut. As shown in this patent, the top of the nut when seated often does not remain extending or protruding above the surface of the metal support plate, but protrudes from the bottom side of the plate or sheet.
On the other hand, some nuts when seated within the aperture are flush with both the upper and lower surfaces of the sheet or support plate in which the nut is seated, such as for example fasteners (mounted-nuts) of the Southco Inc. company as typical of such prior art. The upper edge of some of this particular company's fasteners include the above-discussed hexagonal shape, while others have the generally circular shape but with serrated circumscribing portions. Likewise, the Penn Engineering and Manufacturing Corp. carries both of these types of nuts as fasteners for use in thin panels. U.S. Pat. No. 3,399,705 shows a scolloped wall and downwardly-flanged lip.